Apparatus for stacking or unstacking containers

ABSTRACT

An apparatus which can be converted to either a stacker or an unstacker of relatively heavy objects, such as bins of fruit, that are delivered to and from the apparatus by means of a conveyor. The bins are supported upon dogs which are pivotally mounted upon a pair of carriages positioned at each side of the conveyor. The carriages are slidably mounted upon upright posts and are arranged for joint switch-controlled vertical movement on the posts. This joint movement is provided by vertically extending racks which are attached to the carriages and which are arranged to be driven through pinions affixed to a common horizontal shaft at the top of the apparatus.

United States Patent [191 Westerling Oct. 16, 1973 APPARATUS FORSTACKING OR UNSTACKING CONTAINERS [76] Inventor: David E. Westerling,5936 Meadowbrook Ln., Riverside, Calif.

[22] Filed: Oct. 6, 1971 [21] Appl. No.: 187,042

[52] US. Cl. 214/6 BA, 214/8.5 K [51] Int. Cl. B65g 57/30 [58] Field ofSearch 214/6 BA, 8.5 K, 214/6 P, 8.5 A, 8.5 R

[56] References Cited UNITED STATES PATENTS I 3,466,839 9/1969 Temple214/6 BA 3,325,021 6/1967 Burns et a1. 214/6 BA 3,421,638 l/1969 Lockeet a1. 214/6 BA 3,478,897 11/1969 Dykeman 214/6 BA 3,039,625 6/1962Bruce 214/6 BA FOREIGN PATENTS OR APPLICATIONS Australia 2 l4/8.5 K

3/1967 Great Britain 214/6 BA 9/1965 France 214/6 BA PrimaryExaminer-Robert J. Spar Attorney-F. W. Anderson et a1.

[5 7] ABSTRACT An apparatus which can be converted to either a stackeror an unstacker of relatively heavy objects,

such as bins of fruit, that are delivered to and from the apparatus bymeans of a conveyor. The bins are supported upon dogs which arepivotally mounted upon a pair of carriages positioned at each side ofthe conveyor. The carriages are slidably mounted upon upright posts andare arranged for joint switch-controlled vertical movement on the posts.This joint movement is provided by vertically extending racks which areattached to the carriages and which are arranged to be driven throughpinions affixed to a common horizontal shaft at the top of theapparatus.

10 Claims, 30 Drawing Figures PATENTEDEIBTISIQTS 3.765.546

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' sum 01 or 13 PAIENIElJnm 1 6 ma SEE! 08ff13 z a a M w M: 0% 1 .2 m: mA B 4 a c o C 7 m m A wwu 1 Q o m m o Q. H G M 1L I m P LCMH v F l P i Am c A H w a s m m m w i ,1 M -U 4 w L o w v L c Q RESET PULSEPATENIEDUCI 16 I975 SHEET 100F13 PAIENIEDncI 16 ms SHE] 110! 13APPARATUS FOR STACKING OR UNSTACKING CONTAINERS BACKGROUND OF THEINVENTION 1. Field of the Invention In general, the present inventionpertains to that field of art concerned with apparatus for stacking orunstacking articles, and more particularly, it pertains to apparatus forstacking or unstacking relatively heavy articles, such as bulk fruitbins, which are conveyed to and from the apparatus by means of ahorizontally arranged conveyor.

2. Description of the Prior Art Apparatus for automatically stacking orunstacking relatively heavy objects have been used in many industriesfor a long period of time because of the obvious need for mechanizationin the handling of such loads. For example, in the fruit packingindustry fruit is normally brought into the packing house in large 25bushel bins each of which may carry a load of three-quarters of a ton ormore of fruit. In order to facilitate the storage of these binsand toreduce the overall'handling costs, the bins are normally stacked threeor four high. When certain operations prior to stacking, such as washingor pre-grading, are to be performed upon the fruit, the bin stacks mustbe broken down and then reformed. In the past many different types ofcase or container stacking mechanisms have been used to perform thesefunctions, but none have proven to be entirely acceptable to the fruitpacking industry primarily because of lack of durability and ruggedness,excessive maintenance requirements, or unusually high initial costs dueto bulky and/or complex structure.

The conventional container stacking or unstacking apparatus is providedwith opposed pairs of pivotable dogs which are positioned upon carriagesmounted for vertical movement. The carriages are arranged at oppositesides of the fruit containers so that the containers can be lifted andlowered both individually or in groups, and a transport conveyor isprovided for jointly controlled operation with the stacking orunstacking apparatus to bring the containers into and out of theirstacking or de-stacking positions. By programming the vertical movementof the dogs and providing sensing means for detecting the position ofthe containers, the aforedescribed apparatus can be used to either stackor unstack containers or, in some instances, to do both.

One of the typical means by which the aforedescribed dogs are poweredtolift or lower the containers isby the use of hydraulicor pneumaticcylinders which may be arranged at one or both sides of the transportconveyor'to directly control the movement of the lifting carriages. Suchapparatus is shown, for example, in the prior U.S. Pats. to Vann et al.No. 2,885,111, Hallenius No. 2,931,524, Russell et al. No. 3,053,402, orSchmid No. 3,086,665.

Another common manner in which the container lifting dogs are mountedfor vertical movement is by means of endless chains arranged at theopposed sides of the stacking or unstacking apparatus. Such a method isutilized, for example, in the apparatus disclosed in the prior U.S.Pats. to Huisking No. 2,897,949, Russell No. 2,948,382, or Burns et al.No. 3,325,021.

Other methods of lifting and lowering the container supporting dogsinclude the use of vertically extending arms positioned at opposed sidesof the stacking or unstacking apparatus which are driven through a crankmechanism as shown, for example, in the prior U.S. Pat. to Adams No.2,769,570. Also, fruit boxes have been stacked by means of a pair ofvertically extending screws arranged at opposed sides of the apparatuswhich screws are threadedly connected with the lifting dogs as shown,for example, in the prior U.S. Pat. to Daves et al. No. 2,609,111.

While the aforementioned devices have generally performed their intendedstacking or unstacking functions in an acceptable manner, it will benoted that the devices generally include structure which is relativelycomplex or bulky and, therefore, expensive to manufacture. In the fruitpacking industry, where handling costs must be kept to a minimum, therehas for many years been a need for a relatively simple and inexpensivestacking and unstacking apparatus which will be rugged enough to handlethe relatively heavy loads imposed by bulk bins but which will notinvolve complex or otherwise expensive components.

Another problem, which is prevalent with most of the aforementionedstacking or unstacking apparatus, is the fact that a great deal ofmaintenance is necessitated when the mechanisms for performing thestacking and unstacking operations are complex or are subject tomechanical failure. For example, the various hydraulic and pneumaticcircuitry involved in the elevator mechanisms for the stackers andunstackers are frequently subject to breakdown. Also, the endless chainmechanisms and similar devices are frequently subject to damage due tomisaligned loads. in the fruit packing industry particularly where aperishable product is involved, the delays accompanying a breakdown inthe container handling equipment often prove to be intolerable.

SUMMARY OF THE INVENTION light weight construction and does not includeany.

complex or bulky components. The apparatus is relatively inexpensive tomanufacture andoperate eventhough it is designed to handle particularlyheavy loads such as the large bulk fruit bins used in the fruit packingindustry. 1

, The apparatus of the present invention is designed to operate incombination with a horizontally oriented conveyor which both'brings thecontainers" to be stacked or de-stacked into the apparatus anddischarges them therefrom. ln the case wherein the apparatus of thepresent invention comprises an unstacker, the conveyor individuallyremoves the lowermost container from a stack of containers while theupper bins are elevated and held by the vertically movable containersupport fingers. In the case wherein the apparatus of the presentinvention comprises a stacker, the conveyordelivers individualcontainers to the apparatus while the vertically movable containersupport fingers elevate and retain those containers previously delivereduntil they can be deposited atop the lowermost container.

Basically, the apparatus of the present invention comprises a pair ofupright posts arranged at opposed sides of the container transportconveyor. Carriages are mounted for vertical travel on the posts and arearranged to carry the pivotable fingers which are positioned so as to bereceived under the containers for lifting or lowering them. Eachcarriage is connected to a vertically extending rack. A motor isdrivingly connected to a shaft which is provided with a pair of pinionsengaged with the vertically extending racks. Consequently, when themotor is driven, the racks are moved upwardly or downwardly to, in turn,move the container or containers upwardly or downwardly in the desiredmanner.

With the rack and pinion drive of the present invention thestacker-unstacker apparatus is provided with strength and ruggedness andyet with a minimum amount of structure and a minimum amount ofcomplexity so that servicing problems are virtually eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a binstacker and a bin unstacker constructed in accordance with the teachingsof the present invention. and arranged in a bin handling line whichincludes a bin dumping mechanism positioned between the two devices.

FIG. 2 is a side elevation of the unstacker shown in FIG. 1.

FIG. 3 is an end elevation of the unstacker of FIG. 2 taken in thedirection of the arrows 33.

FIG. 4 is a side elevation of the stacker shown in FIG. 1.

FIG. 5 is an end elevation of the stacker shown in FIG. 4 taken in thedirection of the arrows 5'5.

FIG. 6 is an isometric view of the upper portion of the stacker orunstacker particularly illustrating the rack and pinion drive means forthe apparatus of the present invention.

FIG. 7 is an enlarged vertical section taken along the line 7-7 of FIG.6.

FIG. 8 is an enlarged plan taken in the direction of the arrows 8-8 ofFIG. 6.

FIG. 9 is an isometric view illustrating one of the lift mechanisms usedin the stacker as shown in FIGS. 4 and 5.

FIG. 10 is an isometric view illustrating one of the lift mechanismsused in the unstacker as shown in FIGS. 2 and 3 with the containersupport fingers being shown in their lowered or lifting position.

FIG. 1 1 is an isometric view ofa portion of one of the lift mechanismsfor the unstacker similar to FIG. 10 but showing one of the fingers inits elevated or inoperative position.

FIG. 12 is an enlarged side elevation of the lift mechanism for thestacker particularly illustrating, by means of phantom lines, the mannerin which the support fingers are pivoted to permit the mechanism to bemoved downwardly past an underlying container.

FIG. 13 is an enlarged isometric view of one of the carriages and itsmanner of mounting upon the vertical support post.

FIGS. 14, 15 and 16 are diagrammatic side elevation views illustratingthe operation of the support fingers for the unstacker including,particularly, the manner in which the fingers are cammed inwardlybetween the stacked containers to lift the upper containers from thelowermost container.

FIG. 17 is a schematic representation of the electrical circuitry forthe unstacker of FIGS. 2 and 3.

FIG. 18 is a schematic representation of the electrical circuitry forthe stacker of FIGS. 4 and 5.

FIGS. 19-24 are diagrammatic end elevation views of the unstacker ofFIGS. 2 and 3 illustrating the operation thereof.

FIGS. 25-30 are diagrammatic end elevation views of the stacker of FIGS.4 and 5 illustrating the operation thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now more particularlyto FIG. 1, the apparatus of the present invention is there shown asembodied in an unstacker 32 and a stacker 34. The stacker and unstackerare shown in an operational arrangement wherein they are both arrangedto receive bins of fruit to stack and unstack the same respectively. Ahorizontally oriented conveyor 36 is adapted to carry a stack of bins tothe unstacker 32 which is operated to successively lift the top bin orbins and allow the lowermost bin to be delivered forwardly (in thedirection of the arrow) to processing apparatus such as the bin dumper38 which is arranged to accommodate the singulated bins. The dumper,which is a conventional piece of equipment, forms no portion of theapparatus of the present invention, and its structure and operation willtherefore not be described herein. The singulated bins are removed fromthe dumper and are transported forwardly by a second horizontallyoriented conveyor 40 which is aligned with the conveyor 36 and whichdelivers such bins to the stacker 34. The stacker is operated to receiveeach bin and place it at the bottom of an accumulated stack of binsuntil such time as the requisite number of bins have been thus stacked.At such time the full stack is discharged forwardly by the conveyor 40in the direction of the arrow (FIG. 1).

While the stacker 34 and usntacker 32 perform distinctly differentoperations, each embodies the basic structure of the present invention.As will be pointed out in greater detail hereinafter, one can beconverted to the other by merely repositioning the container and liftmechanism sensing devices and by modifying the structure of the liftmechanisms. As can be seen from FIGS. 2 through 5, the containertransport conveyors 36 and 40 are conventional conveying means comprisedof a pair of endless conveyor chains 41 arranged to run in paralleltracks 41a and to support the bulk bins or containers B on their uppersurfaces. The conveyors are separately driven by conventional electricmotor drive means 42 (only one of which is shown in FIG. 1)'which areelectrically controlled through sensing relays so that they may bestopped and started in response to conditions existing in the stackerand unstacker, all as will be explained in greater detail hereinafter.

Referring now more particularly to FIGS. 2 and 3, which show theunstacker 32, and to FIGS. 4 and 5, which show the stacker 34, it willbe seen that each structure comprises a pair of upright tubular supportposts 50 which are mounted upon a generally rectangular base framestructure 51 that also serves to support the transport conveyors 36 or40. The posts 50 extend upwardly on both sides of the associatedconveyor, and

they are connected across the top by a tubular cross frame member 53.

As particularly shown in FIG. 6, the cross frame member 53 at the top ofthe apparatus is provided with a pair of rigidly attached angle brackets54 at each end thereof with the brackets being, in turn, rigidly securedto the uppermost ends of the posts, 50. The brackets serve to rotatablysupport a drive shaft 56 which extends parallel to the cross framemember and is spaced outwardly therefrom. The cross frame member alsocarries a support plate 58 at one end thereof upon which is mounted areversible drive motor 60 that is in driving engagement with the driveshaft through a drive chain 61 and associated sprockets. Attached toeach end of the drive shaft are a pair of pinions 62 which are arrangedto engage a pair of vertically extending racks 64. As particularlyillustrated in FIGS. 7 and 8, each rack is adapted to ride between theouter face of the associated angle bracket 54 and the inner face of asmall plate 66 which is secured in spaced relationship to the anglebracket by means of bolts 67 which extend through cylindrical spacermembers 68 at the upper and lower ends of the plate. Located betweenthese spacer members and extending inwardly from the angle bracket 54and the plate 66 are a pair of stud shafts 70 each of which rotatablysupport a washer 71 and a roller 72 at the inner end thereof. As'shownin FIG. 8, each rack is provided with a wear strip 74 along the rearwardface thereof which strip is arranged to engage and be guided by therotatable washers 71 at the outer edges thereof. The wear strip is alsoarranged to engage the rollers 72 along the face thereof so that thevertical movement of the rack will be smooth and so that good drivingengagement between the pinion and rack will be assured. As shown in FIG.7, the rollers 72 are offset in the vertical plane to further insure astable support for the drive connection to the racks.

The wear strips 74 which extend downwardly from the racks 64 (as shownfor example in FIGS. 2 or 4) are adapted to be bolted to verticallyextending link members 76'the lower ends of which are connected tocarriages 78 one of which latter structures is shown in detail'in FIG.13. The'carriages, which are adapted to carry the container liftingmechanisms, are arranged to be received upon the tubular posts 50 sothat they may jointly move in the vertical plane as the racks are movedin response to rotation of the drive shaft 56. In order to provide forthis. movement, each post 50 is provided with six guide strips 80 whichare positioned in pairs on three sides of the post so as to formvertical guide tracks 82 therebetween. Each carriage comprises acage-like structure formed of a pair of side plates 84 which areconnected at one end by a pair of support blocks 86. The other end ofeach of the support plates 84 is provided I with a laterally extendingear 87 to which a base plate 88 is bolted -by means'of bolts 89. Thelift mechanism 90 for the unstacker or 92 for the stacker (to bedescribed presently) are adapted to be bolted to the outwardly extendingface of the base plate 88 by the aforedescribed connecting bolts 89.Attached at the top and bottom of the side plates 84 and centrally ofeach of the support blocks 86 are shoulder bolts 94 having cam followerrollers 96 rotatably received at the outer ends thereof. As will beapparent'from FIG. 13, each of the cam follower rollers are arranged tobe received in the tracks 82 so as to roll upon the inner surfaces ofthe guide strips 80 during vertical movement of the carriage wherebyample support is provided for the carriage so that it may move easily asthe supporting rack is driven.

The lift mechanisms and 92 for the unstacker and stacker, respectively,are attached to each of the vertically reciprocable carriages 78 and areshown in detail in FIGS. 9, l0 and 11. Each lift mechanism 90 (FIGS. 10and 11) will be seen to include an angle support member 100 which isattached, by means of the bolts 89, to the face plate 88 of theassociated carriage 78. Support blocks 102 are attached to the inwardlydirected face of the angle support member and serve to rotatably supporta shaft 104 which extends in a horizontal plane transversely of theassociated post 50 and spaced inwardly therefrom. Rigidly attached tothe shaft 104 between each of the end pairs of support blocks 102 are apair of fingers 106. A pair of counterweight members 108 are attached tothe outer ends of the shaft 104 so as to normally cause the fingers 106to be pivoted upwardly (to the position shown in FIG. 11) until theyengage the upper edge of the angle support member 100. In this positionthe fingers will be clear of the path of the containers in the unstackerso that they can move upwardly past the lowermost container in thestack.

Positioned at the center of the shaft 104 andrigidly attached thereto isa projecting finger 109. As the carriages 78 are moved upwardly to aposition just above the lowermost container the fingers 109 are adaptedto be engaged by a pair of vertically extending cam members 110 (FIG. 3)which are attached in spaced relationship to the mounting posts 50 andextend parallel thereto. Rotation of the finger 109 by the lower end acam member 110 will cause the fingers 106 to be pivoted downwardly (tothe position shown in FIG. 10) until they are received'upon stops 103attached between each pair of support blocks 102.

When the fingers 106 are pivoted by the cam members 110, the liftmechanisms will be in a position whereby the fingers will be projectedinto a space between the lowermost container B and the containerdirectly thereabove. This operation is shown diagram.- maticallyin FIGS.14 and 15. Continued upward movement of the carriages (FIG. 16) willresult in the lifting of the uppermost containers leaving the lowermostcontainer on the transport conveyor 36. By means to be describedpresently, the lowermost container can then be removed from theunstacker and the supported containers can be lowered back to theconveyor by the carriages. Continued downward movement of the carriageswill free the supporting fingers 106 from thecontainers and allow thecounterweights 108 to bring the fingers back to their normal upwardlypivoted position (FIG. 11) wherein they can again be movedupwardly torepeat the aforedescribed procedure.

The lift mechanism 92 of the stacker is similar to the lift mechanism 90for the unstacker in that it utilizes pivotally mounted fingers 120.However, the normal position of the stacker container support fingers isas shown in FIG. 9 wherein they are oriented in a horizontal plane. Eachfinger 120 is pivotally. mounted upon the associated lift mechanism bymeans of laterally extending pintles 122 which are rotatably received inspaced support blocks 124. A pair of support blocks 124 are attached toeach end of an angle support bracket 126 so as to pivotably mountafinger 120 at each end thereof. In the aforesaid normal position of thefingers, the outer ends thereof will be engaged by the lower surface ofthe associated support bracket 126 to maintain them in a horizontalplane while they receive the load of the stacked containers upon theinner ends thereof (FIG. 12). The support bracket 126 is adapted to bebolted to the base plate 88 of one of the carriages 78 by the connectingbolts 89 as in the manner of mounting of the unstacker lift mechanism90.

When the carriages 78 are located below a container on the transportconveyor 40, the fingers 120 will assume their normal position as shownin FIG. 9. The carriages can then be moved upwardly and the containerwill be received upon the fingers and lifted thereby. The container canthen be elevated to a position wherein a second container can be broughtin by the transport conveyor to a position directly below the liftedcontainer. The carriages can then be moved downwardly to place thelifted container on top of the second container. This downward movementwill cause the lower face of each of the fingers 120 to engage a topedge of the lowermost container to thereby pivot the fingers upwardlyuntil they are rotated out of the path of the descending containers.Continued downward movement of the carriages allows the fingers to slidedownwardly past the containers until the carriages are again positionedbelow the lowermost container. This process can be repeated until a fullstack of containers has been accumulated. The pivoting movement of thefingers 120 during the downward travel of the carriages is shown in thefull and phantom line illustrations of FIG. 12.

In both the stacker 34 and the unstacker 32 the lift mechanisms 92 and90, respectively, are designed to operate with containers which aresupported on runners so that a space in which the lift fingers can bereceived will exist between each pair of containers in the stack. In theevent that a different type of container is used the lift mechanisms mayhave to be redesigned so that the fingers will be capable of movingbetween the containers.

In order to adapt the stacker 34 and the unstacker 32 for theirrespective functions, control systems are provided which generallycomprise a series of sensing elements for detecting certain criticallocations of the containers and the lift mechanisms. These sensingelements control electrical circuitry which, in turn, controls the drivefor the transport conveyors 36 and 40 and the carriage drive motor 60.In the unstacker (FIGS. 2 and 3), a photoelectric cell P1 is provided tosense the presence of more than one container B in the unstackingapparatus. The photocell P1 and its associated reflector 130 are mountedin depending fashion from a pair of brackets 132 that are attached tothe upright posts 50 and extend outwardly therefrom-in the downstreamdirection (FIG. 2). It will be recognized that the photocell and lightsource are provided at one side of the conveyor with the reflectorpositioned at the other side of the conveyor in a position so that thephotocell will sense the presence of the next to the lowermost containerin the stack when such container breaks the reflected light beam. Also,a second photoelectric cell P2 and its associated reflector 130 aremounted upon a pair of support brackets 134 which are attached to thebase frame 51 of the unstacker. The photocell P2 is located downstreamof the stack (FIG. 2) and is designed to sense the discharge of acontainer from the stack. The base frame 51 also mounts an upright post140 to which there are attached four limit switches LS-l, LS-2, LS-3 andLS-4. The limit switches are arranged to be actuated during the verticaltravel of the carriages by means of actuators 142 and 144 which areattached to one of the upwardly extending links 76. As shown in FIG. 2,the actuators extend laterally of the link so as to engage the actuatingarms on the limit switches during the vertical travel of the carriages.

In the stacker 34, as shown in FIGS. 4 and 5, a photoelectric cell P3and its associated reflector 130 are mounted at the base of theapparatus upon support brackets 134 attached to the base frame 51.Photocell P3 is thereby located so as to sense the presence of acontainer in the stacking zone of the apparatus. A second photoelectriccell P4 and its associated reflector 130 are supported from brackets 146which are attached to the mounting posts 50 and extend outwardlytherefrom in the downstream direction (FIG. 4). The photocell P4 isarranged to sense the uppermost container in a stack of containers whensuch stack comprises a full load so as to initiate the discharge of thestack. As shown in FIG. 4, the fourth container at the top of the stackwould, through photocell P4, indicate that a full stack has beenaccumulated. Finally, a third photoelectric cell P5 and its associatedreflector 130 are positioned across the delivery conveyor 40 at theentrance of the stacker. This photocell serves to permit the delivery ofa container to the stacker after the carriages have begun their upwardmovement but prevents the entry of the container into the stacking zoneuntil the carriages are stopped in their elevated position.

Operation of the stacker 34 and unstacker 32 will be describedparticularly with relation to the operational views of FIGS. 19 through24 (for the unstacker) and FIGS. 25 through 30 (for the stacker) takenin conjunction with the electrical circuitry shown in FIG. 17(unstacker) and FIG. 18 (stacker). In the electrical circuitry shown,each relay has been given the designation RY followed by a particularnumber. The contacts which are actuated by a particular relay aredesignated with the letter C followed by the same number as theirassociated relay. In the event that there is more than one contactassociated with a single relay, the separate contacts are distinguishedby the addition of a letter to the numeral designation. For example, therelay RY-l, shown in FIG. 17, has associated therewith the normally opencontacts C-lA and C-lB, the normally closed contacts C-lC and C-ID, andthe normally open contact C-lE.

In the operation of the unstacker 32, a stack of bins B1, B2, B3 and B4(FIG. 19) are delivered by the trans port conveyor 36 into the stackingzone between the two upright posts 50. Before the stack enters thestacking zone the lift mechanisms will have moved from their lowermostposition, as shown in FIG. 19, to an upper position just below the cammembers where the lift fingers 106 are still retained in their outwardlypivoted positions. When a stack of containers is received in thestacking zone its presence will be indicated by the photocell P1. Thebreaking of the light beam to photocell P1 will deenergize the relayRY-7 to close the normally closed contact C-7 and thereby energize loadin relay RY-l. The energization of relay RY-l closes the normally opencontact C-lB to complete a circuit to the relay RY-S. The relay RY-Scloses appropriate contacts in the drive motor 60 to cause the driveshaft 56 to rotate in a direction so as to pull the carriages 78upwardly. Upon initiation of the upward movement of the carriages thecams 110 will cause the support fingers 106 to be pivoted inwardlybetween the lowermost container B1 and the container B2 thereabove, asshown in FIG. 20. Continued upward movement will occur until theuppermost actuator 142 engages the uppermost limit switch LS-4. Thisopens the circuit to the relay RY-S and stops the drive motor 60 and theupward movement of the carriages. The deenergization of the relay RY-5also closes the normally closed contact C-SC and completes the circuitto the relay RY-6 through contact C-lB, G15, and C-2C. The relay RY-6 isprovided with appropriate contacts which cause the drive motor for thetransport conveyor 36 to be actuated so that the lowermost container B1is driven out from the stack while the other containers B2, B3 and B4remain suspended in the elevated position. As the container B1 leavesthe unstacker, the

beam to photoelectric cell P2 is broken to deenergize relay RY-8. Thiscloses contact C-8 and energizes relay RY-9 which, in turn, closescontact C-9A and opens contact C-9B. The closing of contact C-9Acompletes.

a circuit to relay RY-ll which closes holding contacts C-llA and C-llB.When the trailing edge of the container Bl clears the photoelectric cellP2 the relay RY-8 will again be energized to deenergize the relay RY-9to open contact C-9A and close contact C-9B. The relay RY-ll will remainenergized for a brief period of time while the capacitor C1 dumps itscharge through the relay and the series resistor R1. During this timethe circuit to reset pulse relay RY-l0 is complete through closedcontact C-llB and a contact C-10B is closed to complete a circuit to therelay RY-3. This, in turn, closes contact C-3B to complete a circuit tothe relay RY-4. The relay RY-4 closes appropriate contacts in thecircuitry for the drive motor 60 to reverse the motor and cause thecarriages 78 to be moved downwardly. Thus, the containers B4, B3 and B2will be moved downwardly to the underlying conveyor to the positionshown in FIG. 21. Before the carriages get to their lowermost position,the limit switch LS-l will be closed by the actuator 144 to complete acircuit to the relay RY-2 which opens the contact C-2C to break thecircuit to the conveyor forward" relay RY-6 so that no furthercontainers will be moved-into the unstacker while the stack is down.When the carriages get to their lowermost position and the liftingfingers are automatically dropped to their outwardly pivoted positions,as shown in FIG. 21., the carriages will automatically be againelevated. The carriages will be lifted and the fingers will be cammedsoas to lift the. uppermost containers B3 and B4 from the lower containerB2 allowing it to be discharged from the apparatus with theaforedescribed' process being repeated as shown in FIGS. 22, 23 and 24until the last container B4 is discharged therefrom. During the lastoperating cycle, when the carriage is in the down position and the lastcontainer B4 is discharged from the apparatus, the carriages will againbe elevated even though the load in relay RY-l will be deenergized sincea circuit will be completed through the normally closed contact C-2B andthe closed limit switch LS-4 to the carriage up relay RY-S. However,before the carriages get to the uppermost position, the limit switchLS-4 will be opened to break this circuit and stop the carriages in aposition just before the fingers are cammed inwardly. The apparatus willremainin this condition until a new stack is brought into the apparatusto energize the load in relay RY-l and cause the continued upwardmovement of the carriages to the uppermost position all as describedhereinbefore. Special pushbuttons FBI and PB2 are provided in the eventthat it is desired to manually lower or elevate the carriages.

The operation of the stacker 34 is shown diagrammatically in FIGS. 2530with the electrical circuitry therefor being schematically shown in FIG.18. Initially the conveyor 40 is operated through energization of relayRY-l8 so as to bring a container B5 into the stacking zone (FIG. 25), itbeing understood that conveyor forward relay RY-18 closes contacts'inthe conveyor drive motor to cause the conveyor to be activated. Once thecontainer is received within the apparatus the beam to the photoelectriccell P3 will be broken to deenergize relay RY-l9 and close the contact019. With the carriages 78 in their lowermost position, section LS-6A oflimit switch LS-6 will be closed by the lowermost actuator 144 so thatthe closing of contact C-19 completes a circuit to the relay RY l4through normally closed contacts C-17A and C-l5 and the normally closedlimit switch section LS-7A. The relay RY-l4, through appropriatecontacts, activates the drive motor-60 so that the carriages areelevated to pick up the container B5. Energization of relay RY-l4 alsoenergizes holding relay RY-l3 to close contact C-l3A and maintain thecircuit to the up relay RY-14 even after the limit switch section LS-6Ais opened. As the carriages move upwardly the actuator 142 will closelimit switch LS-S to complete acircuit to the relay RY-12 closingcontact C-l2B. This provides a circuit to the conveyor forward relayRY-18 to permit th I conveyor to bring a second container B6 into theapparatus while the lowermost container B5 is elevared to the uppermostposition (FIG. 26). When the carriages reach the uppermost positionwherein the top actuator 142 opens the section LS-7A of the top limitswitch LS-7, the circuits to the relays RY-12, RY-l3 and RY-l4 arebroken to stop the upward movement of the carriages. A circuit to therelay RY-lS will subsequently be completed when the contact C-19 isclosed. This contact will be closed bythe deactivation of photocell P3by the container B6 when it reaches the stacking position and theresultant deenergization of relay RY+19. When this occurs the downwardmovement of the carriages is initiated since the down relay RY-IS closesappropriate contacts, which reverse the drive motor 60 and, therefore,reverse the direction of movement of the carriages. Also, the conveyorforward" relay RY-l8 is deenergized by the opening of contact C-l6B.Relay RY-l5 is maintained in an energized condition during downwardmovement of'the carriages by a holding relay RY-l6 similar to theholding relay RY- 13. As the carriages move downwardly the top containerB5 will be deposited atop the lower container B6, as shown in FIG. 27.When the carriages arrive at their lowermost position the process willagain be repeated to pick up the containers B5 and B6 to allow a thirdcontainer B7 to enter the apparatus as shown in FIG. 28. The process isagain repeated to allow a fourth container B8 to enter the apparatus asthe containers B5, B6 and B7 are elevated by the carriages. However,with the elevating of the top three containers to allow the stacker toreceive the container B8 (FIG. 29), the uppermost container B5 willbreak the beam to the photoelectric cell P4 to deenergize relay RY-20.This closes contact C-20 so that when the carriages get to the uppermostposition and the limit switch section LS-7A is closed, the full loadrelay RY-17 will be energized. Energization of relay RY-17 opens contactC-l7A to prevent the carriages from moving upwardly again by opening thecircuit to the relay RY-14. However, the carriages are moved downwardlyby energization of relay RY-lS, and the top three containers will bedeposited upon the lowermost container B8 as shown in FIG. 30. When thecarriages arrive at their lowermost positions the limit switch sectionLS-6C is opened and the relays RY- and RY-l6 are deenergized. Thiscloses the contact C-l6B and completes a circuit to the relay RY-l8 todrive the conveyor 40 forwardly to permit the full stack to bedischarged from the apparatus. The photoelectric cell P5 is providedacross the entrance to the stacking apparatus so that if a containerbreaks the beam to thereby deenergize relay RY-21 the contact C-21 willbe opened to break the circuit to the conveyor drive relay RY-l8 duringupward movement of the carriages so that the container entering thestacking apparatus will not collide with the containers being elevated.If it is desired to manually elevate or lower the carriages, pushbuttonsP83 and P84 are provided for this purpose.

By the foregoing description it will be appreciated that a stacker orunstacker apparatus is provided which is of lightweight construction butwhich will function efficiently and require little or no maintenance.Even though the structure of the present invention is lightweight andnon-complex, it is rugged and durable and capable of handling heavyloads such as the bulk fruit bins normally stacked and unstacked incommercial fruit packing operations.

Although the best mode contemplated for carrying out the presentinvention has been herein shown and described, it will be apparent thatmodification and variation may be made without departing from what isregarded to be the subject matter of the invention.

What is claimed is:

1. Apparatus for stacking or unstacking containers comprising conveyingmeans arranged in a generally horizontal plane, a pair of vertical postsone being mounted adjacent each opposed side of said conveying means,control means for bringing said containers to a position adjacent tosaid posts, a carriage mounted for vertical movement on each post ofsaid pair of posts, each of said carriages including pivotably mountedlift fingers movable between a first position wherein they projecttoward said conveying means to receive and support a lower surface ofone of said containers and a second position wherein they are out of thepath of drive means arranged to rotate said shaft so as to jointly movesaid carriages and said one container vertically while said container issupported on said lift fingers.

2. Apparatus according to claim 1 including vertically extending guidetracks provided on each of said posts, each of said carriages beingprovided with inwardly projecting guide means arranged to be received insaid tracks.

3. Apparatus according to claim 2 wherein said guide means compriserollers mounted for free rotary movement.

4. Apparatus according to claim 1 wherein each of said racks extendupwardly adjacent to one of said posts and wherein said shaft is locatedin a generally horizontal plane at the top of said apparatus.

5. Apparatus according to claim 4 including roller guide means forsupporting the upper end of each of said racks.

6. Apparatus according to claim 1 wherein said lift fingers arepivotally mounted upon said carriages for movement between a firstposition wherein said fingers extend inwardly in a generally horizontalorientation to engage and support said containers and a second positionwherein said fingers are pivoted upwardly so that they are out of thevertical path of travel of said containers in said apparatus.

7. Apparatus according to claim 6 wherein said first position of saidfingers is the normal position thereof when said fingers are not inengagement with one of said containers, said fingers being arranged tobe pivoted to said second position by engagement with one of saidcontainers upon downward movement of the associated carriages, andcontrol means for operating said drive means so that said apparatus isprogrammed to stack successive containers delivered thereto by saidconveying means.

8. Apparatus according to claim 7 wherein said control means foroperating said drive means includes means for sensing the presence of acontainer on said conveying means between said posts and means forsensing the presence ofa container near the upper ends of said posts.

9. Apparatus according to claim 6 wherein said second position of saidfingers is the normal position thereof when said fingers are not inengagement with one of said containers, stationary cam means for pivoting said fingers to said first position upon upward movement of theassociated carriages, and control means for operating said drive meansso that the apparatus is programmed to successively elevate all but thelowermost container in a stack of containers to permit said lowermostcontainer to be moved from said stack by said conveying means until eachof the containers in said stack has been individually moved from saidapparatus.

10. Apparatus according to claim 9 wherein said control means foroperating said drive means includes means for sensing the presence of acontainer atop the lowermost container in said stack and means forsensing the discharge of .the lowermost container from said apparatus.

1. Apparatus for stacking or unstacking containers comprising conveyingmeans arranged in a generally horizontal plane, a pair of vertical postsone being mounted adjacent each opposed side of said conveying means,control means for bringing said containers to a position adjacent tosaid posts, a carriage mounted for vertical movement on each post ofsaid pair of posts, each of said carriages including pivotably mountedlift fingers movable between a first position wherein they projecttoward said conveying means to receive and support a lower surface ofone of said containers and a second position wherein they are out of thepath of the containers, a vertically extending rack connected to each ofsaid carriages, each rack extending parallel to and being supported byits associated post for vertical movement relative thereto, eachcarriage including a mounting frame structure which encompasses theassociated post upon which it is mounted whereby all forces other thanvertical forces which are imposed on said carriages will be transferredto said posts rather than to said racks, said posts and racks comprisingthe sole support means for said carriages, a shaft having a pair ofpinions thereon arranged to engage said racks, and drive means arrangedto rotate said shaft so as to jointly move said carriages and said onecontainer vertically while said container is supported on said liftfingers.
 2. Apparatus according to claim 1 including verticallyextending guide tracks provided on each of said posts, each of saidcarriages being provided with inwardly projecting guide means arrangedto be received in said tracks.
 3. Apparatus according to claim 2 whereinsaid guide means comprise rollers mounted for free rotary movement. 4.Apparatus according to claim 1 wherein each of said racks extendupwArdly adjacent to one of said posts and wherein said shaft is locatedin a generally horizontal plane at the top of said apparatus. 5.Apparatus according to claim 4 including roller guide means forsupporting the upper end of each of said racks.
 6. Apparatus accordingto claim 1 wherein said lift fingers are pivotally mounted upon saidcarriages for movement between a first position wherein said fingersextend inwardly in a generally horizontal orientation to engage andsupport said containers and a second position wherein said fingers arepivoted upwardly so that they are out of the vertical path of travel ofsaid containers in said apparatus.
 7. Apparatus according to claim 6wherein said first position of said fingers is the normal positionthereof when said fingers are not in engagement with one of saidcontainers, said fingers being arranged to be pivoted to said secondposition by engagement with one of said containers upon downwardmovement of the associated carriages, and control means for operatingsaid drive means so that said apparatus is programmed to stacksuccessive containers delivered thereto by said conveying means. 8.Apparatus according to claim 7 wherein said control means for operatingsaid drive means includes means for sensing the presence of a containeron said conveying means between said posts and means for sensing thepresence of a container near the upper ends of said posts.
 9. Apparatusaccording to claim 6 wherein said second position of said fingers is thenormal position thereof when said fingers are not in engagement with oneof said containers, stationary cam means for pivoting said fingers tosaid first position upon upward movement of the associated carriages,and control means for operating said drive means so that the apparatusis programmed to successively elevate all but the lowermost container ina stack of containers to permit said lowermost container to be movedfrom said stack by said conveying means until each of the containers insaid stack has been individually moved from said apparatus. 10.Apparatus according to claim 9 wherein said control means for operatingsaid drive means includes means for sensing the presence of a containeratop the lowermost container in said stack and means for sensing thedischarge of the lowermost container from said apparatus.